Determination of incorporated amounts of poly(ethylene glycol)-derivatized lipids in liposomes for the physicochemical characterization of stealth liposomes

• Published in: International journal of pharmaceutics Vol. 203; no. 1; pp. 255 - 263
• Main Authors: Shimada, K, Matsuo, S, Sadzuka, Y, Miyagishima, A, Nozawa, Y, Hirota, S, Sonobe, T
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 10.08.2000; Elsevier
• Subjects: Biological and medical sciences; Calibration; Diglycerides - analysis; General pharmacology; Lipids - analysis; Liposomes; Liposomes - chemistry; Medical sciences; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Physicochemical characterization; Poly(ethylene glycol); Polyethylene Glycols - analysis; Physicochemical characterization; Poly(ethylene glycol); Liposomes; Ethylene oxide polymer; Pharmaceutical technology; Chain length; Dosage form; Liposome; Phospholipid; Drug carrier; Surface analysis; Complex lipid; Chemical synthesis; Density; Physicochemical properties
• ISSN: 0378-5173; 1873-3476
• DOI: 10.1016/S0378-5173(00)00466-X

We describe a method for determining incorporated amounts of poly(ethylene glycol) (PEG)-derivatized lipids in liposomes for the physicochemical characterization of PEG-coated liposomes. This method is based on the spectrophotometric determination of complexes of polyethers with sodium ions after their extraction as picrates into 1,2-dichloroethane, developed by Favretto for measuring levels of polyoxyethylene alkylphenyl-ether non-ionic surfactants in waste water. The same assay was applied to the estimation of PEG-derivatized lipids in liposomes and percent incorporation of PEG-derivatized lipids into liposomes was successfully determined. To prevent the interference from liposomal lipids other than PEG-derivatized lipids in this assay, liposomal samples were diluted at least to a concentration of less than 0.2 mM. The percent incorporation of PEG-lipids varied, depending on the molecular weight of PEG and anchor acyl chain length in PEG-lipids and it was suggested that the percent incorporation of PEG-lipids into liposomes would be a good parameter of quality control of PEG-liposomes in manufacturing facility and the picrate method used in the present study allows for the determination of this parameter without the need for hazardous radioisotopes.